It is well known in the art to prepare elastomers through addition reaction between organopolysiloxanes having a vinyl group attached to a silicon atom and organohydrogenpolysiloxanes having a hydrogen atom attached to a silicon atom in the presence of platinum catalysts. A variety of compositions were proposed in conjunction with this reaction. Cured products of these compositions, however, are difficult to firmly adhere to substrates of metals, glass, rubber and plastics. Undesirably, cured silicone rubber can peel off particularly when used in coating, sealing and potting of electronic parts.
For obviating this drawback, a variety of adhesion modifiers were developed as proposed in Japanese Patent Publication (JP.B) Nos. 13508/1978, 26376/1983, and 5219/1984. Although silicone compositions can be substantially improved in adhesion by adding such adhesion modifiers, their adhesion available with low-temperature curing or high-temperature brief curing is still insufficient.
Some of the above-mentioned silicone compositions are used as transparent adhesives free of fillers such as silica for the purpose of taking advantage of the self-adhesiveness and colorless clarity of the silicone base polymer. The addition of an adhesive modifier to these compositions can lead to a partial loss of clarity because the adhesive modifier is not well compatible with the silicone base polymer.
There is a need for an organopolysiloxane composition capable of forming an elastomer of quality having improved adhesion and tack.